1840, "concurrence, coincidence," literally "a jumping together," formed on model of resilience from Latin consilient-, from assimilated form of com "with, together" (see con-) + salire "to leap" (see salient (adj.)).
word-forming element meaning "together, with," sometimes merely intensive; it is the form of com- used in Latin before consonants except -b-, -p-, -l-, -m-, or -r-. In native English formations (such as costar), co- tends to be used where Latin would use con-.
1560s, "leaping," a heraldic term, from Latin salientem (nominative saliens), present participle of salire "to leap," from a PIE root of uncertain form (source also of Sanskrit sisarsi, sisrate "to flow, run, hurry;"Greek hallesthai "to leap," Middle Irish saltraim "I trample," Middle Welsh sathar "trampling").
The meaning "pointing outward" (preserved in military usage) is from 1680s; that of "prominent, striking" first recorded 1840, from salient point (1670s), which refers to the heart of an embryo, which seems to leap, and translates Latin punctum saliens, going back to Aristotle's writings. Hence, the "starting point" of anything.
<a href="https://www.etymonline.com/word/consilience">Etymology of consilience by etymonline</a>
Harper, D. (n.d.). Etymology of consilience. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/consilience