Source

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late Middle English: from Old French sours(e ), past participle of sourdre ‘to rise’, from Latin surgere .

wiktionary

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From Middle English sours, from Old French sorse(“rise, beginning, spring, source”), from sors, past participle of sordre, sourdre, from Latin surgō(“to rise”), which is composed of sub-(“up from below”) +‎ regō(“lead, rule”), ultimately from Proto-Indo-European *h₃réǵeti(“to straighten; right”), from the root *h₃reǵ-. See surge.

etymonline

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source (n.)

mid-14c., "support, base," from Old French sourse "a rising, beginning, fountainhead of a river or stream" (12c.), fem. noun taken from past participle of sourdre "to rise, spring up," from Latin surgere "to rise, arise, get up, mount up, ascend; attack," contraction of surrigere, from assimilated form of sub "up from below" (see sub-) + regere "to keep straight, guide" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule"). Meaning "a first cause" is from late 14c., as is that of "fountain-head of a river." Meaning "person or written work supplying information or evidence" is by 1777.

source (v.)

"obtain from a specified source," 1972, from source (n.). Related: Sourced; sourcing.