means A spoken or written commitment to do (or not do) something, binding you to a future action others may hold you to.

from From Latin 'promissum,' the neuter past participle of 'promittere' — to send forth, to let go ahead — built from 'pro-' (forward) plus 'mittere' (to send, the same root that fires off 'missile' and 'mission'). So a promise is literally something you've sent ahead of yourself into the future. It reached English through Latin, settling into the language by the late medieval period as both noun and verb.