Webster's Revised Unabridged Dictionary · 1913

Ally

Ally ({not transcribed}) , transitive verb

[Old English alien, Old French alier, French alier, from Latin alligare to bind to; ad + ligare to bind. Compare Alligate, Alloy, Allay, Ligament.]

1.
To unite, or form a connection between, as between families by marriage, or between princes and states by treaty, league, or confederacy; -- often followed by to or with.
O chief! in blood, and now in arms allied. — Pope
2.
To connect or form a relation between by similitude, resemblance, friendship, or love.
These three did love each other dearly well, And with so firm affection were allied. — Spenser
The virtue nearest to our vice allied. — Pope

Ally is generally used in the passive form or reflexively.

Ally ({not transcribed}) , noun

[See Ally, v.]

1.
A relative; a kinsman. [Obsolete] — Shakespeare
2.
One united to another by treaty or league; -- usually applied to sovereigns or states; a confederate.
The English soldiers and their French allies. — Macaulay
3.
Anything associated with another as a helper; an auxiliary.
Science, instead of being the enemy of religion, becomes its ally. — Buckle
4.
Anything akin to another by structure, etc.

Ally ({not transcribed}) , noun

See Alley, a marble or taw.