strain (v.)

c. 1300, streinen, "tie, bind, fasten, gird;" early 14c., "confine, restrain" (a body part, animal, etc.), senses now obsolete, from present-participle stem of Old French estreindre "bind tightly, clasp, squeeze," from Latin stringere (2) "draw tight, bind tight, compress, press together."

This is reconstructed to be from PIE root *streig- "to stroke, rub, press" (source also of Lithuanian strėgti "congeal, freeze, become stiff;" Greek strangein "twist;" Old High German strician "mends nets;" Old English streccian "to stretch;" German stramm, Dutch stram "stiff").

Strain is attested from late 14c. as "tighten; stretch, extend; make taut; stretch to the utmost tension," also, intransitive, "exert oneself, strive; exert a compelling force;" also "overexert (a body part), injure by overstretching."

The sense of "press through a filter, put (a liquid) through a strainer" to purify from extraneous matter is from late 14c. (implied early 14c. in strainer); that of "to stress beyond measure, carry too far, make a forced interpretation of" is from mid-15c. Related: Strained; straining.

Transitive strain at "make a difficulty of" (1580s) echoes Matthew xxiii.24 (strain at a gnat; Tyndale has the line as Ye blind guides, which strain out a gnat, and swallow a camel), in which the sense seems to be "will strain the liquor if they find (but) a gnat in it."

1550s, "injury to a muscle or tendon caused by straining," from strain (v.). The meaning "a stretching or deforming force or pressure" is by 1580s. Paired alliteratively with stress (n.) by 1842; they are from the same Latin verb.

The meaning "passage of music" (1570s) probably developed from the notion of a "tightening" of the voice to sing it; the verb had been used in a literal sense in reference to the strings of a musical instrument by late 14c. Hence, generally, "tone, style, turn of expression" (1620s).

"line of descent, lineage, breed, ancestry," c. 1200, from Old English strion, streon "a begetting, procreation," also "a gain, acquisition, treasure;" from Proto-Germanic *streu-nam- "to pile up" (from PIE *streu-, extended form of root *stere- "to spread").

Hence "race, stock, line" (early 14c.). Applied to animal species from c. 1600; usually involving fairly minor variations, but not distinct from breed (n.). Of microbes by 1897. The general sense of "sort, kind, style" is from 1590s. Normal sound development would have yielded *streen, but the word was altered in late Middle English, apparently by influence of strain (n.1).