*weghs
Your reference said only "ibid", which doesn't mean anything to me. If it's some kind of abbreviation, it should be clarified so that everyone can understand it.
I cited Watkins 1962 and gave the full bibliographical details. Please check again. ibid is a very well known bibliographic abbreviation as you could find out here
I stumbled across this thread, and reading through, I wondered too at your meaning. While ibid is indeed known well enough in various other works, the specifics of how Wiktionary function can make it risky to assume that ibid will always be correct in its particular context.
For instance, suppose the list of descendants were sorted alphabetically by language name. If your line for Old Church Slavonic were placed above your line for Sanskrit, the ibid ceases to make any sense. Alternatively, suppose some other language were inserted between the two, and the new line includes a different citation.
If you intended for your second citation to simply refer to the first, try using the name="xyz" attribute on the <ref> tag instead, and simply use the same value for both attributes. So long as there is one <ref> tag on the page with the same name and full details, the other instances of that identically-named <ref> tag can be empty.
What you had:
* Sanskrit [[avākṣam]]<ref>Watkins, Calvert, 1962, Indo-European Origins of the Celtic Verb. 1. The Signmatic Aorist. p. 19 et passim</ref> * Old Church Slavonic [[vĕsŭ]]<ref>ibid</ref>
A suggested change:
* Sanskrit [[avākṣam]]<ref name="Watkins_1962">Watkins, Calvert, 1962, Indo-European Origins of the Celtic Verb. 1. The Signmatic Aorist. p. 19 et passim</ref> * Old Church Slavonic [[vĕsŭ]]<ref name="Watkins_1962"/>
This way, both citations safely refer to the same source, no matter where the individual <ref> tags appear on the page. HTH!