RUDE. A word found in 2 Corinthians 11:6 (KJV) and in Ecclesiasticus 8:4 (KJV). It does not mean boorish or discourteous, but untrained and unskilled. When Paul wrote that he was “rude in speech,” he did not mean that he was unrefined and boorish, but that he was inexpert and lacking in technical training. The RSV has “unskilled in speaking.”

International Standard Bible Encyclopedia (1915)

rood: Not "impolite" in English Versions of the Bible (except perhaps 2 Macc 12:14), but "untrained," "ignorant"; compare the modern phrase, "a rude drawing." So Sirach 8:4 (apaideutos) and 2Co 11:6 (idiotes, `though I lack technical training in rhetoric’); compare the King James Version and the Revised Version margin Sirach 21:24.