I read gib-cat, as 'gib' never occurs alone. We surely would not say a tom for a tom-cat, a jack for a jackass, a jackdaw, etc. See Introd. p. [58].
Act IV.
Sc. 1.
"So haply Slander,
Whose whisper o'er the world's diameter," etc.
The happy suppliance of Theobald, universally adopted with the change of his for to so.