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Old English wilcuma, exclamation of kindly greeting, from earlier wilcuma (n.) "welcome guest," literally "one whose coming is in accord with another's will," from willa "pleasure, desire, choice" (see will (v.)) + cuma "guest," related to cuman (see come). Cf. Old High German willicomo, Middle Dutch wellecome. Meaning "entertainment or public reception as a greeting" is recorded from 1530. You're welcome as a formulaic response to thank you is attested from 1907. Welcome mat first recorded 1951; welcome wagon is attested from 1961.
Old English wilcumian, from wilcuma (see welcome (n.)). Related: Welcomed; welcoming.