The spelling of the word "tangum" may seem strange to some, but it can be explained through the use of IPA phonetic transcription. The pronunciation of "tangum" is /tæŋəm/, with the first syllable being stressed and the "g" being pronounced as a "ŋ" sound, which is also known as a velar nasal. The spelling "um" at the end of the word represents the vowel sound "əm", which is commonly used in the English language to represent a schwa sound followed by the consonant "m".
There doesn't appear to be any widely recognized etymology for the word "tangum". It does not correspond to any known English word or have a clear linguistic origin. It is possible that the word is a neologism, a made-up word without a specific etymology. Without additional context or information, it is difficult to provide a more definitive answer.