bundling

verb
The practice of wrapping one person in a bed accompanied by another.

Bundling used to be a widely diffused Welsh custom before marriage. The betrothed or engaged pair went to bed, or more frequently lay together, in their clothes . . . Even among families of good position it is tacitly recognized and tolerated, and it was at the outset the product of a clothed state, where touch had to play the part of sight in the unclothed.
– W. C. Hazlitt’s Faith and Folklore of the British Isles, 1870

Practiced in America on a scarcity of beds where, on such an occasion, husbands and parents frequently permitted travellers to bundle with their wives and daughters.
– Capt. Francis Grose’s Classical Dictionary of the Vulgar Tongue, 1796