According to the nonce borrowing hypothesis (NBH), "[n]once borrowings pattern exactly like their native counterparts in the (unmixed) recipient language" (Poplack & Meechan, 1998a, p. 137). Nonce borrowings (Sankoff, Poplack & Vanniarajan, 1990, p. 74) are "lone other-language items" which differ from established borrowings in terms of frequency of use and recognition. Lone other-language items are singly occurring words from the "donor" language which are preceded and followed by words or phrases from the "recipient" language. Whether such other-language words belong only to the donor language (and are classed as codeswitches) or to both the donor and the recipient language (and are classed as borrowings) is both a theoretical and a practical issue. Poplack & Meechan (1998a) suggest that this question can be settled by measuring the linguistic integration of donor-language words, so that infrequent donor-language words which behave like their recipient-language counterparts are categorised as (nonce) borrowings. This suggests that frequency of use need play no role in the extent to which other-language items are linguistically integrated into the recipient language. We challenge this hypothesis with an analysis of soft mutation on English-origin verbs in Welsh, which shows that integration is related to frequency.