c. 1300, "tie, bind, fasten, gird," from present participle stem of Old French estreindre "bind tightly, clasp, squeeze," from Latin stringere (2) "draw tight, bind tight, compress, press together," 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").
From late 14c. as "tighten; make taut," also "exert oneself; overexert (a body part)," Sense of "press through a filter, put (a liquid) through a strainer" is from early 14c. (implied in strainer); that of "to stress beyond measure, carry too far, make a forced interpretation of" is from mid-15c. Related: Strained; straining.
"injury caused by straining," c. 1400, from strain (v.). The meaning "passage of music" (1570s) probably developed from a verbal sense of "to tighten" the voice, which originally was used in reference to the strings of a musical instrument (late 14c.).
"line of descent, lineage, breed, ancestry," c. 1200, from Old English strion, streon "a gain, acquisition, treasure; a begetting, procreation," 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.). Normal sound development would have yielded *streen, but the word was altered in late Middle English, apparently by influence of strain (n.1).