Actually, they captured York (Eoforwíc/Jórvík) in 867 AD after defeating the kings of Northumbria, and Ipswich (Gippeswíc) in 869 AD when they attacked and killed King Edmund the Martyr of East Anglia. Also, for those who didn't ask, the letter 'g' in Gippeswíc was palatalised as [j] before and after front vowels and 'c' was palatalised as [tʃ] in the same positions. That's why place-names south of the Humber have more 'ch' sounds like -chester and -wich, as opposed to the hard Gs and Ks up north which were influenced by Old Norse like -caster, -wik/-wyke and 'kirk' instead of 'church'.
I wondered who'd spot that. I deleted the bit that said 'some claim that' at the start in the hope somebody would pick up on it so I didn't look like the only trivia geek, and then do exactly what you have done, and add some more too it, so cheers.
I'd actually argue the original Old Norse name for York would've been *Jǫfurvík, as a direct translation of Old English Eoforwíc meaning 'boar-bay'. Jǫfurr means boar, but was also a poetic term or 'kenning' for king or ruler in Old Norse. In the 13th century, the Icelandic dialect of Old Norse tended to lengthen some short vowels like ǫ and o to ó and drop certain consonants, and since 13th century Iceland is where most written Old Norse sources come from, the form likely evolved from Jǫfurvík > Jórvík and the meaning was analogised to 'stallion bay' since jór means stallion.
You see the same thing happen to other names in 13th century Old Icelandic. Early Old Norse Norðvegr becomes 13th century Old Icelandic Nóregr, with lengthening of vowels and dropping of some consonants. I'll stop now
I saw a map somewhere that had the most common names for each Country, and because I'm as sad as I'm forgetful, I meant to google why Iceland's was something like Johndotter, as in John's daughter, whereas other places would have Johnson.