Clare/de Clare and Sinclair Surnames

Clare
Irish and English: habitational name from Clare in Suffolk (probably named with a Celtic river name meaning ‘bright’, ‘gentle’, or ‘warm’). One of the first Normans in Ireland (1170–72) was Richard de Clare, Earl of Pembroke, better known as ‘Strongbow’, who took his surname from his estate in Suffolk.
English: habitational name from Clare in Oxfordshire, named with Old English cl?g ‘clay’ + ora ‘slope’.
English: from the Middle English, Old French female personal name Cla(i)re (Latin Clara, from clarus ‘famous’), which achieved some popularity, greater on the Continent than in England, through the fame of St. Clare of Assisi. See also Sinclair.
English: occupational name for a worker in clay, for example someone expert in building in wattle and daub, from Middle English clayere, an agent derivative of Old English cl?g ‘clay’.

Sinclair
Scottish (of Norman origin): name of a powerful Scottish clan, originally a habitational name from Saint-Clair-sur-Elle in La Manche or Saint-Clair-l’Évêque in Calvados, so called from the dedication of their churches to St. Clarus (see Clare 3).
Jewish: Americanized form of some like-sounding Ashkenazic Jewish surname.

Dictionary of American Family Names, Oxford University Press, ISBN 0-19-508137-4