Ebla

mi-nu /minnu/ - from (Tonietti 1997:83‒84, Archi 2002:13‒14, Kogan–Krebernik 2021b: 682)

Different from mi-in ‘in, at’ at least synchronically.

PWS
*min - from (Arakelova 2001:39, Kogan 2015: 91–92)
Lipiński (1997:465) traces this preposition back to the PS root *mny ‘to count, to measure’, which is highly improbable (Arakelova 2001:41).