It's a comma instead of a dot. Viking's sentence should say: Only Estionian [is related]. Lithuanian and Latvian are Indo-European and thus not related.
It's entirely possible that those false friends has a common origin, but have drifted apart with time. For example, English has borrowed the Nordic word for stairs (trappa) twice. A "stair door", aka trap door is the older word, but (possibly due to some accidents, or more probable, a similar method came up in animal traps), trap got it's current meaning a few centuries later.
Second time is for a specific geological formation (trap rock or trapp).
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