Part of speech: Particle, enclitic
Inflection: Indeclinable = Indeclinable word (preposition, conjunction, ...)
Streitberg 1910, p. 61 – facsimile | text
-hun Enklitikon [Enklitikon, Indefinita bildend: s. ains-, ƕan-, ƕas-, ƕeilo-, manna-, þis-hun.]