I said Chandas is the foot of the Vedapurusa. Poetry also has its foot. In tamil poetry there are "iradikkural" (stanzas with two feet), naladiar(stanzas with four feet), etc: "adi" here has the same meaning as "pada", that is foot. Naladiar does not mean four adiyars. Great devotees are called adiyars because they lie at the lotus feet of the Lord. (In Sanskrit too we have similar terms like "Acaryapada", Govindapada", and "Bhaghavatpada". Naladiar means stanzas with four feet.
If "foot" is called "pada" or "pada" in sanskrit, it is known as "adi" in tamil. (It goes without saying that "foot is the English equivalent) A stanza must have a certain number of feet and its metre must have a certain number of letters or syllables. "Pada", "adi", "foot"--thus all languages have words with the same meaning to denote a line of a stanza. The realisation that there is something common to all mankind, something that shows the unity of the human race, is inwardly satisfying.
One-fourth of a mantra or a stanza is called a "pada". In Tamil one out of four parts is called "kal"(that is foot). The foot ("leg")forms one-fourth of the human body. From the head to the waist is one half of the body, and from the waist to the feet is another half. And half of the latter half, i.e. one fourth is "kal" in Tamil or foot(leg). The waist is called "arai" in that language, meaning half.
In Tamil "kal" usually means the entire leg and "padam" or "padam" is used to denote the foot. But in some contexts kal is used in the sense of the foot. For instance, in terms "ullangal" and "purangal" (sole and upper part of the foot respectively) only the foot is referred to. In Sanskrit too "pada" means both leg and foot.
For a general background, please see here