From миш (miš, “mouse”) (dated) + -ца (-ca), a calque of Latin mūsculus.
ми́шца • (míšca) f
- (dialectal) muscle
- Synonym: (standard) му́скул (múskul)
- “мишца”, in Речник на българския език [Dictionary of the Bulgarian Language] (in Bulgarian), Sofia: Bulgarian Academy of Sciences, 2014
- “мишца”, in Речник на българския език [Dictionary of the Bulgarian Language] (in Bulgarian), Chitanka, 2010