The compound adjective 'two-day-old' is a modern English formation built entirely from native Germanic elements. Its logic is transparent and arithmetic: it combines the numeral 'two', the unit of time 'day', and the adjective 'old' to specify an exact age or duration. Each component retains its core meaning from Old English, with 'old' in this construction shifting from a general sense of age to a precise function following a number and a time unit. This pattern exemplifies the analytic and compounding nature of English, creating a clear, descriptive term without the need for classical affixes, directly communicating the literal concept of something that has reached an age of two days.

Structure: two (number) + day (unit of time) + old (having a specified age) - two: From Old English 'twā', feminine and neuter of 'twēgen' (two). A numeral root. - day: From Old English 'dæg', meaning a 24-hour period or the daylight hours. A noun root. - old: From Old English 'eald', meaning aged, ancient, or of a specified age. An adjective root.