The old name of Zemen was Belovo; it was renamed to Zemen in 1925. The new name was initially only given to the railway station nearby, but it was soon carried over to the village itself. The present name commemorates the medieval castle of Zemlangrad, which was located in the Struma gorge in the vicinity of Zemen. The fortress was first mentioned in the 11th-century Tale of Isaiah as ЗЄМЛЬНЬ ГРАД and as ЗЄМЛЪНЬ in a 15th-16th century Serbian chronicle. The toponym is derived from the Bulgarian word for "land" (земя, zemya) and refers, according to the locals, to the only arable land in the rocky surrounding area.