Prehistory
Twanthain and the surrounding islands were first peopled circa 2400 BC/BCE by Austronesian peoples. Some archeological sites suggest that seashells were used as currency.
Pre-colonial period
The Twanthainese language was not written until the people made contact with the Khmer Empire in 1023 AD/CE, from which they borrowed the Khmer script (ខ្មាឯ ងាព៑, K̃mae n̏ap).
Spanish colonization attempts
The first European contact was by the Spanish in June of 1568, who set up a colony on the main island of Twanthain. These Spanish colonists were assimilated into the native population by March of 1569. The subsequent lack of response to the Spanish mainland prompted them to return to Twanthain in May of 1571 and establish a larger colony; by April of 1575, these new colonists had been assimilated into Twanthainese society as well. Notably, the Spanish governor-general had been given a position in Twanthain's government, but Twanthain retained its independence; unbeknownst to the Spanish crown, Twanthain was not truly colonized but entered a sort of de facto free association with Spain, a ruse maintained by the government successfully until 1821. This second colony led to the development of a Latin orthography for Twanthainese, but the Khmer orthography continued to be used at the same time. Spanish was made a co-official language of Twanthain.
Spanish-Twanthainese War
After the former New Spain gained its independence in September 1821 as Mexico, Spain rechecked all of its colonies that were administered by New Spain. This led to Spain becoming aware of the assimilation of their 1571 colony, and associated deception. Enraged, Spain began a war to conquer Twanthain, which consisted mostly of on-and-off large battles and was harder by Twanthain's mountainous territory. This war lasted from January of 1822 to September of 1829, concluding from a massive battle brought on by Spain's failed reconquest of Mexico. The battle ended in a treaty which involved the partial cession of some Twanthainese territory for a third Spanish colony, Nuevo San Ambrosio (New Saint Ambrose).
Post-colonial period
In December of 1975, after Franco's death in the prior month, Spain ceded the territory of Nuevo San Ambrosio back to Twanthain. Spanish remains an official language of Twanthain today, as it remains among the most spoken languages in Twanthain besides Twanthainese.