late 14c., "small ape or monkey," from Old French marmoset "grotesque figurine; fool, jester" (late 13c.), perhaps a variant of marmote "long-tailed monkey, ape," then, as a term of endearment, "little child." It is said to be from marmonner, marmotter "to mutter, mumble," which is probably of imitative origin. Some French authorities suggest a derivation of marmoset from marmor "marble," as if "little marble figurine." The English word was applied from early 17c. specifically to a type of small squirrel-like South American monkey.

Middle English seme, from Old English  seam, "seam of a garment, suture, junction made by sewing together the edges of two pieces of cloth or two edges of the same piece," from Proto-Germanic *saumaz (source also of Old Frisian sam "hem, seam," Old Norse saumr, Middle Dutch som, Dutch zoom, Old High German soum, German Saum "hem"), from PIE root *syu- "to bind, sew."

Chidynge and reproche ... vnsowen the semes of freendshipe in mannes herte. [Chaucer, "Parson's Tale," c. 1386]

In Middle English also "a gash or scar" (c. 1400). Meaning "raised band of stitching on a ball" is recorded from 1888. Geological sense of "thin strata between two wider ones" is from 1590s. Figurative phrase bursting at the seams, expressive of overfullness, is by 1962. Seam-squirrel "a louse" was old U.S. slang (1893).