It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the clothing of Sayyiduna Adam and Sayyidah Hawwa was of nail (the substance of fingernails). When they ate from the forbidden tree, nothing of that clothing remained on them except the like of a nail; all the rest of it was gone. The two of them began to cover themselves with the leaves of Paradise, that is, fig leaves.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3320