You have probably heard the expression "to dilly-dally" — which means “to dawdle.” Well, if you take the dilly out of dilly-dally to get just dally — you still have pretty much the same meaning. Dally has other common definitions, such as “to flirt” (especially without care of the result) or “to play.” The light tone is probably an echo of its origin, which is likely the French word dalier, meaning “to amuse oneself.”