Origin and Meaning
I have not yet come across convincing evidence of the etymology of our name. It is concievable that the names of different Wardell lines originally had different meanings.
See: The relevance of surnames in genealogy by The Society of Genealogists
Family tradition suggests that the meaning of Wardell of the Yorkshire line might have been: War - Dale
The site clanhuston.com [seems to have disappeared] did not list a suggestion for Wardell but it explained Dale:
Dale is an English place name for the man who lived in the valley, from Middle English dale = dale, valley, from Old English doel and Old Norse dalr. It is also a name that described the man who emigrated from any of the several locations by that name.
See also suggestions by: www.surnamedb.com/Surname/Wardell