Definition from Wiktionary, the free dictionary
Etymology 1 
Old English ġealga.
- Wooden framework on which persons are put to death by hanging.
- (colloquial, obsolete) A wretch who deserves to be hanged.
- (Can we find and add a quotation of Shakespeare to this entry?)
- (printing, obsolete) The rest for the tympan when raised.
- (colloquial, obsolete) suspenders; braces
Derived terms 
wooden framework on which persons are put to death by hanging
Etymology 2 
- Third-person singular simple present indicative form of gallow.