Inevitable, a.
Etymology: [L. inevitabilis: cf. F. inévitable. See In- not, and Evitable.]
1. Not evitable; incapable of being shunned; unavoidable; certain. "The inevitable hour." Gray. It was inevitable; it was necessary; it was planted in the nature of things. Burke.
2. Irresistible. "Inevitable charms." Dryden.
Shades of meaning
Fernald has no entry of its own for inevitable; he lists it under necessary.
Where he writes about it:
Inevitable (L. in, not, and evito, shun) is primarily the exact equivalent of the Saxon unavoidable; both words are applied to things which some at least would escape or prevent, while that which is necessary may meet with no objection; food is necessary, death is inevitable; a necessary conclusion satisfies a thinker; an inevitable conclusion silences opposition. — from necessary