It's actually worse. The name couldn't be from the 1st century CE because otherwise it would be Lonchinus [lɔn'ki:nʊs]; back then Greek still kept ⟨χ⟩ as [kʰ] (as in "kit"), this would only change around the 4th century or so.
Plus whoever coined that name wasn't fully proficient in Greek, otherwise they wouldn't plop a Latin -īnus into it, they'd go with ⟨λογχίτης⟩ lonkhítēs "spear-bearer, the spear guy" → Lonchites instead.
...the English pronunciation stands out as being weirder than everything above. Also, obligatory:
A spear of Longinus a day keeps the Tang sea away~
nickname for Roman soldiers was “Miles” from Latin mille for “thousand” – legionaries walked everywhere giving us the unit of measure, a Roman mile = mille passus (thousand paces)