Trend
Old English trendan ‘revolve, rotate’, of Germanic origin; compare with trundle. The verb sense ‘turn in a specified direction’ dates from the late 16th century, and gave rise to the figurative use ‘develop in a general direction’ in the mid 19th century, a development paralleled in the noun.
wiktionary
From Middle English trenden "to roll about, turn, revolve", from Old English trendan "to roll about, turn, revolve" from Proto-Germanic *trandijaną(“to revolve”). Cognate with Dutch trent(“circumference”). Akin to Old English trinde "ball", Old English tryndel "circle, ring". More at trindle, trundle.
Compare German trennen(“to separate”).
etymonline
trend (v.)
1590s, "to run or bend in a certain direction" (of rivers, coasts, etc.), from Middle English trenden "to roll about, turn, revolve," from Old English trendan "turn round, revolve, roll," from Proto-Germanic *trandijan (source also of Old English trinde "round lump, ball," Old Frisian trind, Middle Low German trint "round," Middle Low German trent "ring, boundary," Dutch trent "circumference," Danish trind "round"); origin and connections outside Germanic uncertain. Sense of "have a general tendency" (used of events, opinions, etc.) is first recorded 1863, from the nautical sense. Related: Trended; trending.
trend (n.)
"the way something bends" (coastline, mountain range, etc.), 1777, earlier "round bend of a stream" (1620s), from trend (v.); sense of "general course or direction" is from 1884. Sense of "a prevailing new tendency in popular fashion or culture" is from c. 1950.
