Is there a pali term for "natural concentration"?

In the book, "Handbook for mankind" Buddhadhasa Bikkhu describes two types of concentration: - One "as a result of organized practice", which he refers to as vipassana-dhura, and is mentioned in post-tipitaka commentaries. - One that "come about naturally". In the text, there are no pali words given for the latter, and the only reference given is that it is described in the Tipitaka. My questions are, - Is there a name in pali for the latter type? - Are there specific descriptions of the second type of concentration somewhere in the tipitaka or elsewhere? (Please note that i'm not asking for the correctness, efficacy, or other evaluations of the statements above. This is primarily a reference request).