Hello ccharles, all,
Perhaps the language of Maghadi was widespread at certain levels of society?
Here is an extract from the BPS book ‘’ The Story of Mahinda, Sanghamitta, and the Sri Maha-Bodhi’’ by Piyadassi Thera:
[……… Although the recorded history of the Sinhalas begins with the landing in Lanka of Vijaya in 543 BCE, the history of Buddhism in Sri Lanka starts with the arrival of the Arahat Thera Mahinda, the son of Asoka the Great. Nevertheless, one cannot justifiably conclude that before the coming of Mahinda Thera, Buddha and His Teachings were altogether unknown to the people of this island. The Sri Lanka Chronicles, Mahavamsa and Dipavamsa and the Samantapasadika, the Vinaya commentary, give vivid descriptions of the Buddha Gotama’s three visits to this island, made in the fifth year, and the eighth year after his Enlightenment.
When Maha Mahinda arrived here in the reign of King Devanampiyatissa, 236 years after the landing of Vijaya, and expounded the Dhamma to the people, they were able to grasp quickly the Message of the Master, which spread throughout this island with surprising speed. This indicates that the sowing ground allotted to Maha Mahinda had already been prepared by reason of earlier contacts with Magadha, where Buddhism flourished. We know that at the request of the ministers of Prince Vijaya, the Pandyan King of Madhura sent his daughter to be the queen of Vijaya. She was accompanied by many maidens from the Pandyan Kingdom, craftsmen, and a thousand families of the eighteen guilds. Now these Pandyans were originally a Ksatriya race of the Aryans from the Madhyadesa, the scene of the Buddha’s lifelong ministry.
We are also told that Panduvasudeva, the nephew and immediate successor of Vijaya, married Bhaddakaccana, the beautiful daughter of the Buddha’s own first cousin, King Pandu. Further, as we know from the Mahavamsa, the non-Buddhist Indian sects like the Niganthas and Paribbajakas were already in Sri Lanka. We must also infer that the contemporaries and the fellow countrymen of the Niganthas also would have been here.
Sri Lanka being very close to the sub-continent of India, there would have been continuous intercourse between the peoples of the two countries. Also, Sri Lanka was often touched by sea-going vessels from India, and we can be sure that Buddhist traders came to this country and spoke of the Buddha and his Teachings to the inhabitants whom they met.
From the history of the Devanampiyatissa period we can gauge that the institutions which prevailed in India’s middle country, Magadha, also prevailed in Sri Lanka. These facts afford abundant evidence that the Buddha and His Teaching were known to the people of this island even before the arrival of the Great Saint Maha Mahinda and his Sister, Theri Sanghamitta ………]http://www.bps.lk/olib/bl/bl057-p.html