The story you may have heardThe extracted draft gave two eastern sources. Spitzer derived the word from Arabic al-qāʾid 'the commander' via Catalan alacay, but alacay is only recorded from 1558, after the Spanish and French words, and the sounds don't fit (TLFi, Corominas). The other theory, Turkish ulak 'courier' through Byzantine Greek, is favoured by FEW and Pfeifer but rests on a misdated 'laquet' in Froissart. Corominas preferred Old Occitan lecai 'glutton'. None is proven.