A corruption of the word Haole, Hawaiian slang for foreigner. Usually applied only to Caucasian people. Not necessarily derogatory, depends on context.
If you look up Haole on urban dictionary and spell it Howlie, you are probably a Haole.
The Urban Dictionary Mug
One side has the word, one side has the definition. Microwave and dishwasher safe. Lotsa space for your liquids.
Buy the mug