Merchant & Marchant often confused for several reasons
1. Dialect - sound similar
2. Marchant derived from French - Marchand. Such names unpopular in UK at this time & often changed to Merchant.
3. Have traced family to William Marchant/Merchant b. 1961, William Marchant/Merchant his son b. 1782 & George Henry White Marchant/Merchant b. 1816.