equal:  Latin aequus (a word of unknown ancestry) meant ‘level’ or ‘even’. From it was derived the adjective aequālis ‘equal’, which has provided the term for ‘equal’ in all the modern Romance languages, including French égal (source of English egalitarian ), Italian uguale, and Spanish igual. English, however, is the only Germanic language in which it constitutes a major borrowing.
English also possesses, of course, a host of related words, including adequate , equanimity , equate , equation  equator  (etymologically the line of latitude that ‘equalizes’ day and night), and iniquity  (etymologically the equivalent of inequality), not to mention all those beginning with the prefix equi-, such as equidistant , equilibrium  (literally ‘equal balance’, from Latin lībra ‘balance’), equinox , equity , and equivalent . => adequate, egalitarian, equator, equity, iniquity
late 14c., "identical in amount, extent, or portion;" early 15c., "even or smooth of surface," from Latin aequalis "uniform, identical, equal," from aequus "level, even, flat; as tall as, on a level with; friendly, kind, just, fair, equitable, impartial; proportionate; calm, tranquil," which is of unknown origin. Parallel formation egal (from Old French egal) was in use late 14c.-17c. Equal rights is from 1752; by 1854, American English, in relation to men and women. Equal opportunity (adj.) in terms of hiring, etc. is recorded by 1925.