The story
From acyclo(guanosine) + -vir (“antiviral”). Analyzable as a- + cyclo- + -vir.
Etymology from Wiktionary, CC BY-SA 4.0.
aciclovir
Today it means: A cyclic synthetic nucleoside C₈H₁₁N₅O₃ used as an antiviral drug (trademarks Avirax, Zovirax) chiefly in the treatment of chicken pox, shingles, the genital form of herpes simplex, and AIDS. Full definition →