From Middle High German gehalt, deverbal from gehalten (“to keep still, retain, preserve, imprison”), itself from halten (“to hold”). The earliest attested sense of the noun is “custody, prison”. In some southern dialects it also means “room, container, closet”. The modern sense develops in the 15th century, at first in the context of coins and metal alloys.

18th century, originally for “pension”. Derived from ge- + halten (here in the sense of “to maintain, keep, support”, cf. unterhalten). Neuter gender is expected when ge- is a nominal suffix (rather than part of the verb stem). However, the masculine was originally predominant, likely by analogy with etymology 1 above. The neuter did establish itself since the 19th century.