Sinclair is from the Norman French Saint-Clair — referring to Saint Clarus or various places in Normandy. Madelaine Petsch's Riverdale character Cheryl Blossom — Cheryl Marjorie Blossom's middle name is Sinclair-derived. Frank Sinclair — multiple historical figures. Sinclair Broadcast Group — major American media conglomerate. Clive Sinclair (1940-2021) — male; English inventor; the Sinclair ZX Spectrum (1982) was one of the most-influential early home computers in the UK; over 5 million units sold worldwide. The Sinclair Clan is one of the most-historically-significant Scottish clans, seat at Rosslyn Chapel — featured prominently in Dan Brown's The Da Vinci Code (2003) which sold 80+ million copies.
Sinclair does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Sinclair reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.