The h was dropped from Shitlington and Sitlington was adopted in 1929 with the approval of the county council.

Investigating the family name Sitlington and came across the village of Sitlington, England.  It was not always so named.  From Wikipedia.  

Sitlington, historically Shitlington, was a township in the ancient ecclesiastical parish of Thornhill in the wapentake of Agbrigg and Morley in the West Riding of Yorkshire comprising the villages and hamlets of Middlestown, Netherton, Overton and Midgley.  The h was dropped from Shitlington and Sitlington was adopted in 1929 with the approval of the county council.  The population of the civil parish at the 2011 census was 5,963.

An understandable decision.