Etymology: < modern French chaise (chaize Cotgrave), a phonetic alteration of chaire (so Pazis for Paris , etc.), established in the ordinary sense ‘chair’, whence by extension ‘sedan-chair’, and by transference a wheeled vehicle for travelling in. In this later sense alone chaise passed into English, notwithstanding that chair had itself here received the same development (see chair n.¹ 11, which however was not always an exact synonym of this word, but often used as the name of a particular sort of chaise). (Cathedra , chair , chaise , are thus all forms of the same word.) The interpretation of the pronunciation /ʃeɪz/ as a plural noun gave rise to an inferred singular /ʃeɪ/: see chay n.², shay n.¹(The change of lingual r to z in French is a phenomenon widely exemplified. It appears fully established at Orleans in 15th cent., but did not come down beyond 1620.)

Etymology: < chaise n.