Old English word "speech, talk, utterance, word," from Proto-Germanic *wurdan (cf. Old Saxon, Old Frisian word, Dutch woord, Old High German, German wort, Old Norse orð, Gothic waurd), from PIE *were- "speak, say" (see verb).
The meaning "promise" was in Old English, as was the theological sense. In the plural, the meaning "verbal altercation" (as in to have words with someone) dates from mid-15c. Word processor first recorded 1973; word processing is from 1984; word wrap is from 1977. A word to the wise is from Latin phrase verbum sapienti satis est "a word to the wise is enough." Word of mouth is recorded from 1550s.