Equivalent

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late Middle English (describing persons who were equal in power or rank): via Old French from late Latin aequivalent- ‘being of equal worth’, from the verb aequivalere, from aequi- ‘equally’ + valere ‘be worth’.

wiktionary

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equi- +‎  -valent. From Latin aequivalentem, accusative singular of  aequivalēns, present active participle of  aequivaleō(“I am equivalent, have equal power”). 

etymonline

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equivalent (adj.)

early 15c., "equal in value, power, or effect," from Late Latin aequivalentem (nominative aequivalens) "equivalent," present participle of aequivalere "be equivalent," from Latin aequus "equal" (see equal (adj.)) + valere "be well, be worth" (from PIE root *wal- "to be strong"). As a noun from c. 1500, "that which is equal or corresponds to." Related: Equivalently.