gratitude [LME] Gratitude, gratify [LME], and grateful [M16th] all go back to Latin gratus ‘pleasing’, gratitude via medieval Latin gratitudo ‘thankfulness’; gratify from combining gratus with facere ‘make, do’; and grateful by way of an obsolete English word grate ‘agreeable’ also derived from the Latin. A related Latin word gratuitus ‘free, spontaneous, voluntary’ gives us two words that have wandered from their original meaning: gratuity [E16th] originally ‘graciousness, favour’, changing to ‘tip, pay’ by 1540; and gratuitous [M16th] originally ‘free’, gaining the sense ‘unnecessary, uncalled for’ before the end of the century.