The word unanimous is reasonably easy to trace: it comes from Latin unum (one) + anima (mind). If several people are of the same unanimous opinion, they could be said to be speaking “of one mind”.
The word equivocal looks very similar. It comes from aequi (same) + vocal (from vox, voice). It would seem that it should mean “speaking with the same voice” and thus have a meaning similar to unanimous. Yet, it means the opposite, and it is unequivocal that is a synonym of unanimous.
How did equivocal manage to reverse its meaning?
Best Answer
Equivocal does not mean the opposite of unanimous, nor has it reversed its meaning.
For a person to equivocate is to use ambiguous language, and be non-committal: to "hedge" between two positions without committing to either, and (literally) to "call equally one thing or the other" — to talk equally of two different positions.
Equivocal is the adjective form: an equivocal statement is one which talks equally of two different things, and does not take a clear single position. Unequivocal is the opposite: something with no ambiguity, something that does not equally emphasise two contradicting points, a strong message which leaves no doubt.
Note that these words are generally used to statements coming from one person; they are not (necessarily) related to whether an opinion is unanimous or not. Unanimous just means, as you said, that everyone shares the same opinion. So, when used for a statement made by a committee, all possibilities exist: it may be
So you see they are orthogonal, not opposites.