pretty + -ly.
prettily (comparative more prettily, superlative most prettily)
- In a pretty manner.
1995 (date of the publication of the anthology), Douglas Adams, The Hitch Hiker's Guide to the Galaxy: a Trilogy in Five Parts, ISBN 0434003484, page 316:
- the butterflies were flitting about prettily, and the whole of nature seemed to be conspiring to be as pleasant as it possibly could.