Is the -old morpheme in 'threshold' an OE locative?

This blog post by Anatoly Liberman gives a recent and comprehensive overview of some of the complications surrounding this word.

In summary, Liberman suggests, following Eduard Sievers, that the word's original etymon was þersc-o-ðl(o). The first part is related to modern thresh ~ thrash. The suffix -ðl(o), which later undergoes metathesis to become -ld, is described by Skeat as usually denoting an agent or implement.

(To me this scenario seems a bit implausible: the semantics of the suffix doesn't fit very well, and the proposed metathesis would have to have taken place independently in Old English and Old Norse in view of the Old Norse cognate þreskjöldr, unless borrowing was somehow involved. But I'm not an etymologist whereas Liberman is, so I'd be inclined to trust him rather than me!)