Assist, v. t. [imp. & p. p. Assisted; p. pr. & vb. n. Assisting.]
Etymology: [L. assistere; ad + sistere to cause to stand, to stand, from stare to stand: cf. F. assister. See Stand.]
To give support to in some undertaking or effort, or in time of distress; to help; to aid; to succor. Assist me, knight. I am undone! Shak.
Syn. -- To help; aid; second; back; support; relieve; succor; befriend; sustain; favor. See Help.
1 other Webster entry under this spelling
Assist, v. i.
1. To lend aid; to help. With God not parted from him, as was feared, But favoring and assisting to the end. Milton.
2. To be present as a spectator; as, to assist at a public meeting. [A Gallicism] Gibbon. Prescott.
Shades of meaning
Fernald has no entry of its own for assist; he lists it under abet, help, promote.
Where he writes about it:
In law to aid or abet makes one a principal. (Compare synonyms for accessory.) To cooperate is to aid as an equal; to assist implies a subordinate and secondary relation. — from help