Definition - Now obsolete, the term was used by philologists to designate what is now called Early Middle English, the English spoken and written between 1100–50 CE and 1250 CE, i.e, the first period of Middle English.

Oxford English Dictionary -
The term's first English citation is from 1735:
"The Nicene…Creed, translated into Semi-Saxon."
(Shelton tr. Wotton's View Hickes' Thes. 100)

Please comment