liniment n.

"Any soft, ropy, glutinous, or viscous substance" [Century Dictionary], Old English slim "soft mud," from Proto-Germanic *slimaz (source also of Old Norse slim, Old Frisian slym, Dutch slijm "slime, phlegm," German Schleim "slime"), which is probably related to Old English lim "birdlime; sticky substance."

This is from a PIE root *(s)lei- "slimy, sticky, slippery" (source also of Sanskrit linati "sticks, stays, adheres to; slips into, disappears;" Russian slimak "snail;" Old Church Slavonic slina "spittle;" Old Irish sligim "to smear," leinam "I follow," literally "I stick to;" Welsh llyfn "smooth;" Greek leimax "snail," limne "marsh, pool, lake," alinein "to anoint, besmear;" Latin limus "slime, mud, mire," linere "to daub, besmear, rub out, erase").

As an insult to a person from mid-15c. Figuratively, of anything clinging and offensive, 1570s. Slime-mold, common name for a type of fungi, is from 1880.