(Northern English) Sulky, moody.
Early 20th century: from dialect mard ‘spoilt’ (describing a child), alteration of marred (see mar).
“If you’re going to be mardy about it I won’t take you!”
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.