also semipermeable, 1873, in reference to a membrane, etc., "relatively permeable," from semi- + permeable. Translating German halbdurchlässig.
Entries linking to semi-permeable
semi-
word-forming element of Latin origin meaning "half," also loosely, "part, partly; partial, almost; imperfect; twice," from Latin semi- "half" (before vowels often sem-, sometimes further reduced to se- before m-), from PIE *semi- "half" (source also of Sanskrit sami "half," Greek hēmi- "half," Old English sam-, Gothic sami- "half").
The Old English cognate, sam-, was used in such compounds as samhal "in poor health, weakly," literally "half-whole;" samsoden "half-cooked" ('half-sodden'), figuratively "stupid" (compare half-baked); samcucu "half-dead," etymologically "half-alive" (see quick (adj.)); and the lingering survivor, sandblind "dim-sighted" (q.v.).
The Latin element was common in formations from Late Latin, as in semi-gravis "half-drunk," semi-hora "half hour," semi-mortuus "half-dead," semi-nudus "half-naked," semi-vir "half-man, hermaphrodite."
The Latin-derived form in English has been active in forming native words since 15c. Semi-bousi "half-drunk" ('semi-boozy'), now obsolete, was among the earliest (c. 1400). As a noun, semi has variously been short for semi-detached house (by 1912), semi-trailer (by 1942), semi-final (by 1942).
permeable adj.
early 15c., "passable" (of an area); "penetrable" (of a building)," from Late Latin permeabilis "that can be passed through, passable," from Latin permeare "to pass through, go over," from per "through" (from PIE root *per- (1) "forward," hence "through") + meare "to pass," from PIE root *mei- (1) "to change, go, move." Meaning "capable of being passed through without rupture or displacement" is from 1773, especially of substances permitting the passage of fluids. Related: Permeably.