Urdu LughatI checked Sukumar Sen's "বাংলা স্থাননাম" (Bengali Toponym). He also has no useful information. Like many other place-names in Bengal, haoRa/হাওড়া (Anglicized: Howrah) is quite opaque.
Thank you for the parallel. While I agree with rehanelbengali that it is unlikely to be directly from the Urdu word, the semantics is intriguing. It would make sense to check in older Bengali sources if there was a word like 'haoRa' (presumably cognate to Urdu hoRaa) which, maybe, signified some sort of merchant boats, and check if they had any special connection to this place - which would not be surprising because there were riverine market places on the opposite bank of the Hoogley where now stands Kolkata.
Could this word be its origins?
হাওড় hāoṛa n. an extensive marsh or quagmire or fen.