Likewise in other lexica. The headword must be quoted from somewhere -- perhaps from its only independent attestation: a fragment of the parodist Hegemon of Thasos [see eta 52, and under tau 599], quoted in Athenaeus, Deipnosophists 15.698E (15.55 Kaibel).
The forms of ei)/somai (and its compounds) are sometimes used in epic as future for ei)=mi "go," which itself serves as a future in Attic. See already under alpha 3138.