The spelling of the word "thickheadednesses" may seem daunting at first glance, but it can be broken down through its phonetic transcription. The word is composed of three parts, "thick," "headed," and "-nesses" which indicates pluralization. The IPA phonetic transcription breaks it down as /θɪk/ + /ˈhɛdɪd/ + /nəsɪz/. "Thick" is pronounced as "thick" with a voiced "th" sound, "headed" is pronounced with a short "e" sound and the "d" is doubled, and "-nesses" is pronounced with a schwa sound followed by "s" and "z."
The word thickheadednesses is a combination of various roots and suffixes.
The base word, thickheaded, combines the word thick, meaning dense or not easily penetrated, and headed, meaning having a head or mind. Thickheaded is often used metaphorically to describe someone who is slow-witted or not quick to understand or perceive things.
The addition of the suffix -ness at the end of thickheaded transforms it into a noun, denoting a state or quality of being thickheaded.
Lastly, the plural form is indicated by the addition of the plural suffix -es to thickheadedness to create thickheadednesses.
Overall, the etymology of thickheadednesses involves the combination of thick, headed, -ness, and -es.