hundredth (adj., n.)
"next in order after the ninety-ninth; an ordinal numeral; being one of one hundred equal parts into which a whole is regarded as divided;" early 14c., "one of 100 equal parts," from hundred + -th (1). According to OED, Old English had no ordinal form. The hymn tune known as Old Hundredth is attested from mid-16c., so called because later it was set to the 100th Psalm in the old numbering of the psalter.
updated on June 23, 2019