Note 376 — Chapter XXVIII · VALHÖLL-VALHALLA.
Reading edition
Einherjar is plural, and is a compound. Ein = only, single; and herjar, from the verb herja = make warfare. Thus it means the only fighters, the only champions, being the warriors chosen by Odin to dwell in Valhalla with him, while Freyja lodged one-half of the slain.