Considering that many IEists believe that there is a succinct possibility of there having been contact between early IE speakers and Semitic speakers, whether direct or indirect, I think that this much neglected subject needs to be explored further. I've always been thrilled by the classic example of Proto-Indo-European (PIE) *septḿ̥ which is a perfectly preserved fossil of Semitic grammar, with *-t- representing the Semitic feminine marker and *-m̥ marking the so-called "mimated" form, presumably a definite marker in function. I then wonder about the potential of Proto-IE and other neighbouring protolanguages to show us snippets of Proto-Semitic grammar in action. Newbies and ultra-conservative IEists may be afraid of these ideas but they have to learn to deal with it because it's not going away. We need to figure out exactly what happened instead of continuing to hold onto and exploit 'mystery' in these areas. Personally, I've developed an elaborate theory based on internal reconstruction of PIE that predicts that Mid IE's counterpart was *séptam with accent originally on the initial syllable. (The accent would later fall on the last syllable because of being affected by the accent of the numeral *h₁októu "eight" but the zerograded last syllable is testimony to its former accentuation.)
There's some confirmation that I might not be offtrack when it comes to another word that I'm really suspecting is a loanword from Semitic into Pre-IE (specifically in Mid IE). While the consonantism for the Semitic verb "to know" is normally reconstructed as *[ydʕ], Old Canaanite Cuneiform Texts of the Third Millennium (1979) speaks on the uncertainty of the root's form on page 193, footnote 11: "It is not clear whether to reconstruct w or y as the initial consonant of the Proto-Semitic root." That's somewhat interesting because if the Semitic root was in fact *[wdʕ], its potential relationship to PIE *weid- becomes stronger.
Based on my theories concerning Mid IE, *waid̰a should be the antecedent form of PIE 3ps *wóide. If so and if it were yet another Semitic loanword, we should expect that this is taken from the Semitic stative form *wadiʕu with accent on the initial syllable because there are no heavy syllables here. That is, there are no non-final syllables of the form CVC or CV: which attract accent from the default initial position in Proto-Semitic as they tend to do in its daughter languages. This correspondence is interesting because it would hint that prepalatalization was heard on the Semitic *-d-. (Note also the correspondence of Semitic *gadyu 'kid, young goat' and PIE *gʰáido- "goat" which also shows a curious metathesis of alveolar stop and glide.) Presumably then, the exact pronunciation of the Semitic word would be *['wæʲdɪʕʊ] and received into MIE as *waid̰a ['wajd̰ə]. This would then imply that perfective *wóid-e came first, and then through the process of ablaut *wēid-ti was formed, in turn becoming present *wéid-e-ti and aorist *weid-t once Anatolian went its seperate way.
I can't believe so few are talking about this. Doesn't anyone else find this fascinating? Doesn't anyone else think that the subject of early Indo-European loans is our priority over reconstructing Nostratic roots blindly and that it's terribly important to Indo-European studies? Drink more coffee, people. There's tonnes more to cover on this topic.
 What I suggest for the stress accent placement of Proto-Semitic is much like in modern Arabic. See Ryding, A Reference Grammar of Modern Standard Arabic (2005), p.37 (link here).
 Whether this metathesis would be due to the peculiar pronunciation of Proto-Semitic speakers themselves or due to inaccurate perception and imitation by Mid IE speakers, such a switch-up in the transmission of a word from one language to the next is perfectly natural and found elsewhere. Darya Kavitskaya in Compensatory Lengthening: Phonetics, Phonology, Diachrony (2002) relates her own story about perceptual metathesis on page 48 in footnote 8: "Indeed, in teaching Russian to American students, I noticed many instances of palatalization of the consonant being heard as some kind of diphthongal property of the preceding vowel, for example, [banʲa] 'bath' was misheard and pronounced as [baʲnʲa] or even [bajna]." (link here).