OED has 3 definitions for Gallow as a verb. It looks like internet has sort of revived an obsolete usage in Hang around.

(Obs.)To hang on a gallows or cross.
Lit. cite: 1400 Leg. Rood Wi grete lewes he is galwed, And dye for Monnes gelte.


(rare)Of a bird: To cluck, to scream. Hence gallowing.
Lit. cite:
1825 HOGG Q. Hynde 80 The capperkailzie scorn'd to flee But gallow'd on the forest tree. 1830 AIRD in Blackw. Mag. XXVIII. 817 Choked shrieks..And gallowing cries..thicken'd the midnight air.

obs. form of GALLY v., to frighten.
1605 SHAKES. Lear III. ii. 44 The wrathfull Skies Gallow the very wanderers of the darke And make them keep their Caues