mid-15c., "good will," from Middle French gratitude (15c.) or directly from Medieval Latin gratitudinem (nominative gratitudo) "thankfulness," from Latin gratus "thankful, pleasing" (from suffixed form of PIE root *gwere- (2) "to favor"). Meaning "thankfulness" is from 1560s.
he was overwhelmed with gratitude for their help
gratification
gratify
gratin
grating
gratis
gratitude
gratuitous
gratuitously
gratuity
gratulate
gratulation