A large passenger boat used on the Nile, typically with lateen sails.
Mid 19th century: from Arabic, literally ‘golden’, denoting the gilded state barge formerly used by the Muslim rulers of Egypt.
“She met him on a dahabeeyah on her Nile cruise and the rest is history!”
With regard to, or at the level of, orders in a taxonomic system; according to an ordinal number, system, etc.; on an ordinal scale; with regard to order.
Mid 19th century; earliest use found in The Edinburgh Review. From ordinal + -ly.