"hanging formation of carbonite of lime from the roof of a cave," 1670s, Englished from Modern Latin stalactites (used 1654 by Olaus Wormius), from Greek stalaktos "dripping, oozing out in drops," from stalassein "to trickle," from PIE root *stag- "to seep, drip, drop" (cognates: German stallen, Lithuanian telziu "to urinate") + noun suffix -ite(1). Related: Stalactic; stalactitic.