Until this week,F.W. Woolworth Co. was a household name to U.S. investors, while Brascan Ltd. was a relatively little known Canadian holding company with interests in Brazil.

But that all changed dramatically this week as Brascan announced a blockbuster $1.1 billion cash bid for the international merchandiser.

Woolworth, the original "five and dime" store chain, is a 100-year-old enterprise with annual sales of more than $6 billion. The $35 a share bid is less than the book value of Woolworth assets and yesterday Woolworth bave its corporate suitor a stinging rebuff.

Woolworth schairman Edward Gibbons denounced the offer and said it raised "moral and ethical questions of a most serious nature," because of the role played by Canadian Imperial Bank of Commerce.

The bank is financing the billion-dollar bid and is also the largest worldwide banker to the Woolworth chain.

Commerce is the second largest of Cananda's charter banks, with assets of $42 billion. It is among the 30 largest banks in the world.

It is providing Brascan with $700 million to finance the $35 a share bid for all the common stock of Woolworth. Gibbons said Commerce has had "full access to the most confidential information with respect to the company's present financial status and future prospects."

He added that the offer raises "substantial legal questions," under state and federal securities laws, including misuse of inside information, margin requirements and disclosure requirements.

Gibbons said the offer is "grossly" inadequate, not in the best interests of shareholders and should be opposed.

At this point Gibbons was only warming up; he said in his opinion the actions of the bank "permeated and tainted the entire offer."

He noted that Brascan was itself the target of a takeover bid by Edpar Equities.

Edpar is a company controlled by members of the Bronfman family, a Montreal-Toronto family which controls the giant worldwide Seagram distilling empire. Patino N.V. of the Netherlands has a one-third interest in edpar.

It has been alleged that the bid for Woolworth is a defensive maneuver by Brascan to avoid being taken over, Gibbons said.

"If ithis charge is correct Woolworth shareholders should be so informed and should not be pawns in defensive actions by Brascan," Gibbons said.

He added that if U.S. rules apply to Brascan, such action would be improper. On a ethical level, Gibbons said, such action would violate international standards.

It is difficult to perceive what contribution Brascan could make to Woolworth in view of its "extremely limited retrail distribution experience," Gibbons said.

Commenting on Brascan's disclosure filing with the Securities and Exchange Commission, he said as a result of the loans necessary to finance its offer, Brascan admits in the filing that it will "have to either borrow an additional $200 million to service the debt or sell off assets."

He suggested that because of Brascan's debt load, if the deal is completed, it might have to strip Woolworth's huge holdings worldwide to meet its financial obligations. This could results in significant loss of jobs and materially damage Woolworth's future prospects, he said.

Gibbon alleged that in view of Brascan's relatively modest size and recent financial history he felt it is "inconceivable that the Commerce would have agreed to lend such a company the enormous sum of $700 million without relying on inside highly confidential information which it received in a fiduciary capacity concerning Woolworth's assets and prospects."

A Commerce spokeman said "we are convinced that our obligation to both sides has been fully satisfied."

The Brascan filling disclosed that three Brascan directors are also on the bank's board. They are R.G. Harrison, the bank's president, J. H. More, Brascan chairman, and lawyer A. J. MacIntosh.

The document states that the bank advised Brascan that "while some officers of the bank may receive information from time to time about the company's (Woolworth) Canadian subsidiary, it has al long-standing bank policy that all information received from borrowers about their business and financial condition must be treated with confidence," and may not be imparted to any third party or used for any other purpose.

It also states that the bank lending officers who gave initial approval of the loan advised Brascan that they had no prior participation in any bank transactions involving Woolworth, had never received any confidential information or documents concerning the credit files in connection with the loan approval.

Harrison was one of the bank officials but did not participate in the loan approval or attend the Brascan meeting that approved the offer.

Brascan chairman Moore said he is "disappointed by the opposition of Woolworth management" to the Brascan bid.

He said there is no basis whatever for "any of the accusations," made by Woolworth management. Brascan remains "determined to move ahead vigorously with its offer and will take all necessary steps to permit the bid to begin as soon as possible. This will let each Woolworth shareholder determine whether or not to accept the offer."

Meanwhile Edper, which has decided not to proceed with a $28 a share bid for control of Brascan, is reviewing its options.

An Edper director, Trevor Eyton, said the possibilities include steps to halt the bid for Woolworth, Edper announced its takeover plans for Brascan on Monday, the same day as the Brascan for bid was made public.

What Edper wanted was a Brascan with more than $400 million in cash-the proceeds of the sale of its Brazilian hydroelectric utility last year-not a company with big debts and a chain of stores. CAPTION: Illustration, WOOLWORTH BUILDING