Step back 50 years, grab your sweetheart, swing to the left, swing to the right, do a little zip zop ... it's the Lindy Hop.

Once the hippest dance of the '30s, and the predecessor to the jitterbug, the Lindy Hop is making a comeback -- thanks to an English dance troupe called the Jiving Lindy Hoppers.

"We've traced it back to its roots," says Hopper manager Terry Monaghan. "It was the first form of swing dance, but in fact it was the culmination of several American dances done to jazz as the music evolved -- ragtime, black bottom, Charleston, tap."

It is said that the Lindy, named after pioneer aviator Charles Lindbergh, first appeared on the dance scene in Harlem in the '30s at such infamous juke joints as the Cotton Club and the Savoy.

Then the war came. And the Lindy died out.

But in 1983, a resurgence began.

"It happened in New York and London and Stockholm," says Monaghan. "People started getting into the original Lindy Hop. Some saw it as a way of creating a social situation. We saw it was a way to have this group."

The Jiving Lindy Hoppers, a troupe of 14, went to New York to learn the intricacies of the dance from veteran hoppers Frank Johnson and Norma Miller. "The rest we've learned from old films," says Monaghan. Now the troupe tours internationally, teaching as well as performing the swing step. "We feel it is an important American tradition that Americans tend to undervalue," says Monaghan.

The Jiving Lindy Hoppers will be performing tomorrow night at the National Museum of Natural History's Baird Auditorium at 7. Tickets are $12 for Resident Associate Program members, $16 for nonmembers. For information, call 357-3030.

They will also be performing Tuesday night at Glen Echo Park's Spanish Ballroom at 7:30. There will be a dance, with instruction, beginning at 8:30. Tickets are $10. For information call 779-0234.