The word "suppliest" is a verb form of "supply," which means to provide something that is needed. The spelling can be broken down using the International Phonetic Alphabet (IPA). The first syllable "sup" is pronounced like "suhp" with a short u sound (sʌp), while the second syllable "-pliest" (or "-plī-est" with a long i sound) is pronounced like "p-lie-est" (plɑɪəst) with a diphthong that combines the sounds of the long i and schwa. Together, the word is pronounced "suhp-lye-est" (səplaɪɛst).
The word "suppliest" is derived from the Middle English word "supplyen", which in turn comes from the Old French word "supplier". This Old French term was originally derived from the Latin word "supplere", which means "to fill up, complete, supply". The suffix "-est" in "suppliest" indicates the third-person singular present form of the verb, which is used in Early Modern English.