strain (v.) Look up strain at Dictionary.com
"to stretch, draw tight," c.1300, from present participle stem of Old French estreindre "bind tightly, clasp, squeeze," from Latin stringere (2) "bind or draw tight," from PIE root *strenk- "tight, narrow; pull tight, twist" (cf. Lithuanian stregti "congeal;" Greek strangein "twist;" Old High German strician "mends nets;" Old English streccian "to stretch," streng "string;" German stramm, Dutch stram "stiff"). Sense of "press through a filter" is from early 14c. (implied in strainer); that of "lay undue stress on, make a forced interpretation of" is from mid-15c. Related: Strained; straining.
strain (n.2) Look up strain at Dictionary.com
"line of descent," Old English strion, streon "gain, begetting," from Proto-Germanic *streun- "to pile up," from PIE root *stere- "to spread, extend, stretch out" (see structure (n.)). Applied to animal species first in c.1600.
strain (n.1) Look up strain at Dictionary.com
"injury caused by straining," 1550s, from strain (v.). The meaning "passage of music" (1570s) probably developed from a verbal sense of "to tighten" the voice, originally the strings of a musical instrument (late 14c.).