'Consonance' is Latin for 'sounding together' — and a consonant literally needs a vowel to sound.
Agreement or compatibility between opinions or actions; in music, a combination of tones that sounds pleasant and stable; in poetry, the repetition of consonant sounds.
From Old French 'consonance,' from Latin 'consonantia' (agreement, harmony of sounds), from 'consonāns' (sounding together), the present participle of 'consonāre' — composed of 'con-' (together, with) and 'sonāre' (to sound). The concept originates in Pythagorean music theory, where certain intervals produced by simple numerical ratios (octave 2:1, fifth 3:2) were deemed consonant because the sound waves 'agreed.' The same Latin root gives English
The grammatical term 'consonant' (as in b, d, g, etc.) comes from the same Latin source: a consonant is a sound that can only be fully pronounced 'together with' (con + sonāre) a vowel. The letter 'b' on its own is nearly silent — it needs a vowel to 'sound together' with. This ancient Latin grammatical insight remains the standard terminology worldwide.