What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
(Characterized by) walking or running sideways; formerly specifically designating a spider of the group Laterigradae (now disused).
Mid 19th century (in an earlier sense). From lateri- + -grade, after post-classical Latin laterigradus, adjective, scientific Latin Laterigradae, former group name (Latreille 1817).