From Medieval Latin 'dictionarium' (a collection of words) — at root, a collection of things pointed out.
A reference work listing words and their meanings, typically in alphabetical order; a book or digital resource explaining the vocabulary of a language.
From Medieval Latin 'dictionarium' (collection of words and phrases), from Latin 'dictio' (a saying, a word), from 'dicere' (to say, to speak), from PIE *deyḳ- (to point out, to show, to say). The PIE root *deyḳ- is highly productive: Latin 'dicere' (to say) gives 'diction', 'dictate', 'edict', 'verdict', 'indicate', and 'index'; Greek 'deiknunai' (to show) gives 'paradigm' and 'apodeictic'; Old English 'tæcan' (to show, to teach) gives the English word 'teach.' The medieval formation 'dictionarium' (c.1220, in Johannes de Garlandia's usage) meant a book
Samuel Johnson took nine years to compile his 1755 'Dictionary of the English Language' — when told that the French Académie's dictionary had taken forty scholars fifty-five years, he replied, 'This is the proportion. Let me see; forty times forty is sixteen hundred. As three to sixteen hundred, so is the proportion of an Englishman to a Frenchman.'