The spelling of the word "coombs" can be explained using the IPA phonetic transcription. The first sound is /k/ followed by a long u sound represented by /uː/. The next sound is a bilabial nasal represented by /m/, and the final sound is a voiceless alveolar fricative represented by /s/. This gives us the phonetic transcription /kuːmz/. When written, the double "o" can be confusing, but it represents the long u sound in this case. The added "s" is for pluralization.
The word "coombs" has two distinct etymological origins.
1) In Old English, the word "cumb" meant a small valley or hollow, and the plural form was "cumbas". Over time, this evolved into "coombs" in Middle English and referred specifically to a deep, narrow valley or a hollow between hills. This sense of the word is primarily used in regional dialects of southwestern England.
2) The word "coomb" also has a separate etymology in relation to hair. In this context, it derives from the Old English word "cumb", which means a comb used for hair. The plural form "cumbas" referred to multiple combs, and in Middle English, it changed to "coombs". This sense of the word is still used today when referring to the thin, flat toothed instruments used for combing or styling hair.