Some help with “hólpinn”

Yesterday, I came across the word “hólpinn” in Icelandic for the first time (that I recall). Tragically, the word came up because people were tweeting about the attacks in Norway yesterday. Fortunately, this word means “safe, secure”, and it was used in a positive context.

Looking at “hólpinn”, it looks a lot like the past participle of a strong verb, having the -inn ending, and also declining as one (note that “-in” is treated as part of the stem, and the masc. sg. acc. matches the nom.):

et.				ft.
	kk.	kvk.	hvk.		kk.	kvk.	hvk.
nf.	hólpinn	hólpin	hólpið	nf.	hólpnir	hólpnar	hólpin
þf.	hólpinn	hólpna	hólpið	þf.	hólpna	hólpnar	hólpin
þgf.	hólpnum	hólpinni	hólpnu	þgf.	hólpnum	hólpnum	hólpnum
ef.	hólpins	hólpinnar	hólpins	ef.	hólpinna	hólpinna	hólpinna

the question then remains, which verb? 

The clue, for me, lay in the verb “to help”, in English.  If I asked you to give the past tense forms of “to help”, you would hopefully respond with “helped” for the simple past (e.g. I helped yesterday) and also for the past participle (e.g. I have helped before).  This is because “to help” is a weak verb in English.  This was not always the case, however.  At one point, “to help” was a strong verb with the past tense “holp” and past participle “holpen” (i.e. I help today, I holp yesterday, I have holpen before). The “-en” ending on strong verbs (e.g. bitten, fallen) is cognate to the “-inn” ending in Icelandic.  Looking at the dictionary entry for “hólpinn”, we can see that it mysteriously points to “hjálpa”, despite the fact that the past participle of “hjálpa” is now “hjálpað”.  At some point in the past, “hjálpa” changed from a strong verb to a weak one, but the past participle stuck around, perhaps because it had this extra meaning that wasn't necessarily attached to the verb itself (this is just my guess, though).

This is a common trend in Germanic languages that can be observed by comparing the inventory of strong verbs across them and seeing that most languages have a weak verb that corresponds with a strong one in another language.  Icelandic, as a more conservative language, has more strong verbs than English, although Icelandic's set of strong verbs does not necessarily contain all of those still strong in English. (I wracked my brain to come up with an example of this and couldn't find one, though I recall that such do exist.  Anyone want to help me out?)