Patti-dāna: lit. 'giving of the acquired', i.e. 'transference of merit.' Though in the older texts very seldom mentioned e.g. A VII, 50, it is, however, a widespread custom in all Buddhist countries. It is presumed that moral merit, especially that acquired through giving food, can be transferred to others, apparently for the reason that one's own good actions may become to others, especially to departed relatives and friends reborn in the ghost realm, an inducement to a happy and morally advantageous state of mind. Transference of merit is advocated though without mentioning the term patti-dāna in the Tirokudda Sutta Khp. and Petavatthu and its Com. Khp. Tr.. It is one of the ten 'bases of meritorious action' puññakiriyavatthu, called there pattānuppadāna.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.