Calculate

google

ref

late Middle English: from late Latin calculat- ‘counted’, from the verb calculare, from calculus ‘a small pebble (as used on an abacus)’.

wiktionary

ref

Borrowed from Latin calculātus, perfect passive participle of calculō(“I reckon, originally by means of pebbles”), from calculus(“a pebble”). Refer to calculus for origin.

etymonline

ref

calculate (v.)

1560s, "to ascertain by computation, estimate by mathematical means," from Latin calculatus, past participle of calculare "to reckon, compute," from calculus (see calculus). Meaning "to plan, devise" is from 1650s; hence "to purpose, intend" and "to think, guess" (1830), both U.S. idioms. Replaced earlier calculen (mid-14c.), from Old French calculer. Related: Calculable.