stillicide (n.)

also distil, late 14c., distillen, "to let fall in drops" (transitive); early 15c., "to drop, trickle, drip, fall in drops" (intransitive), from Old French distiller (14c.), from Latin distillare "trickle down in minute drops," from dis- "apart" (see dis-) + stillare "to drip, drop," from stilla "drop," which is of uncertain origin, perhaps from a PIE root *sti-. De Vaan compares Greek stile "drop;" Lithuanian styri "to become stiff," Old Norse stira "to be rigid, stiff," but has doubts about all of them. From late 14c. as "obtain or extract by distillation;" from c. 1400 as "subject to distillation." Related: Distilled; distilling.

Middle English stif, from Old English stif "rigid, inflexible, not easily bent," in physical senses often suggesting rigor mortis, from Proto-Germanic *stifaz "inflexible" (source also of Dutch stijf, Old Frisian stef, Old High German stif, German steif "stiff;" Old Norse stifla "choke").

The Germanic word is said to be from a PIE *stipos-, from the root *steip- "press together, pack, cram" (source also of Sanskrit styayate "coagulates," stima "slow;" Greek stia, stion "small stone," steibo "press together;" Latin stipare "pack down, compress," perhaps also stipes "post, tree trunk;" Lithuanian stipti "to stiffen, grow rigid," stiprus "strong;" Old Church Slavonic stena "wall"). However Boutkan suggests the possibility that the Germanic words are a metaphoric use from words for staff (n.).

By extension, "strong, violent; difficult to master or overcome:" In reference to battles and competitions, "fierce, stubborn, contested," mid-13c.; of winds or currents c. 1300; of liquor from 1813. In Middle English also "powerful, staunch, unmoving, resolute," and paired alliteratively with strong.

Of substances, "not fluid, thick and tenacious," early 15c. As "not natural or easy in movement," c. 1300. As "rigidly ceremonious, not easy or gracious in manner," c. 1600. To keep a stiff upper lip is attested from 1815. Related: Stiffly.