"ichariba choodee" is indeed an Okinawan expression that can be variously translated in English as "When we meet, we are brothers/sisters", "From the moment we meet, we become family", "If we met before, then we're family", "Once together, friends forever", etc. The idea behind it is that every chance meeting has meaning and every interaction is valuable. Some relate the expression back to the warmth of the Okinawan people and their willingness to welcome others.
The exact expression can be written as follows, depending on the script:
Romaji: ichariba choodee
To deconstruct this, "ichariba" (more literally, "if we meet/met [by chance]") comes from the verb "ichain (行逢ん)" which means "to meet by chance" and "choodee (兄弟)" is the word for "siblings" or "brothers and sisters". Note that the sentence literally reads "If we meet/met, siblings" and that it has no verb. This is because the verb is implied, something you also see in Japanese (e.g. "良いお年を" which means "happy (new) year" is one such case, where the implied verb is "お迎えください" "have a/spend a").
For reference, here's the entry on the expression in Ajima Okinawa, a fairly well-known Japanese-Okinawan online dictionary: https://hougen.ajima.jp/e462
I hope this helps!