Acerbity, n.
Etymology: [F. acerbité, L. acerbitas, fr. acerbus. See Acerb.]
1. Sourness of taste, with bitterness and astringency, like that of unripe fruit.
2. Harshness, bitterness, or severity; as, acerbity of temper, of language, of pain. Barrow.
Shades of meaning
Fernald has no entry of its own for acerbity; he lists it under acrimony.
Where he writes about it:
Acerbity is a sharpness, with a touch of bitterness, which may arise from momentary annoyance or habitual impatience; asperity is keener and more pronounced, denoting distinct irritation or vexation; in speech asperity is often manifested by the tone of voice rather than by the words that are spoken. — from acrimony