The story
- Middle English · inherited fromGod blesse you
- English todayGod bless you
From Middle English God blesse you, God blisse you. A clause in the present subjunctive inherited intact from a time when English was freely productive of it. Diachronically it is not a shortening; synchronically it is often surface-analyzed as such; present-day English has a heavy need for the modal auxiliary (may) to ensure syntactic clarity, whereas earlier English could more easily drop it.
Words from the same roots
Etymology from Wiktionary, CC BY-SA 4.0.