Webster's Revised Unabridged Dictionary · 1913

Ho

Ho , pronoun

In some Chaucer MSS.

Who. [Obsolete]

Ho , noun

[See Ho, interj., 2.]

A stop; a halt; a moderation of pace.
There is no ho with them. — Decker

Also: Hoa

Ho , proper noun

(Chemistry) The chemical symbol for Holmium.

Ho (hō) , interjection

[Compare French & German ho.]

1.
Halloo! attend! -- a call to excite attention, or to give notice of approach.
What noise there, ho? — Shakespeare
Ho! who's within? — Shakespeare
2.
Stop! stand still! hold! -- a word now used by teamsters, but formerly to order the cessation of anything.
The duke... pulled out his sword and cried “Hoo!” — Chaucer
An herald on a scaffold made an hoo. — Chaucer

Also: Hoa