RPTR COULD NOT UNDERSTAND CTLR INSTRUCTIONS; ASKED FOR A REPEAT; STILL WAS UNSURE BUT TAXIED INTO POS AND TOOK OFF WITH TFC ON FINAL.

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AT BNA I WAS INSTRUCTED BY GND CTL TO TAXI TO RWY 2C. DEP CTL FREQS WERE GIVEN; DEP ALT WAS GIVEN. NO CONTACT TWR FREQ WAS GIVEN. AFTER RUNUP WAS COMPLETED; WE CONTACTED DEP ON 119.35 AND WERE TOLD TO HOLD SHORT FOR RWY 2C AND CONTACT THE TWR ON 118.6. I CONTACTED THE TWR ON 118.6 AND TOLD THEM WE WERE READY TO GO. THE TWR REPLIED 'HOLD SHORT.' C130 WAS LNDG ON RWY 2C; OR APPEARED TO BE RWY 2C. THE TWR CALLED AND SAID SOMETHING INDISTINGUISHABLE THAT ENDED WITH GO. I CALLED THE TWR BACK AND ASKED TO SAY AGAIN. THE TWR REPLIED AGAIN WITH SOMETHING I COULD NOT UNDERSTAND. WHAT I THOUGHT I HEARD WAS 'HURRY AND GO; TFC ON A 4 MI FINAL.' I TAXIED ONTO RWY 2C AND TOOK OFF. UPON DOING SO; TWR CALLED AND SAID WE DID NOT HAVE CLRNC TO TAKE OFF; CONTINUE ON; AND TURN TO HDG AND CONTACT DEP. THE PERSON IN THE TWR WAS SPEAKING VERY FAST -- TOO FAST FOR THE AMOUNT OF TFC. THE CTLR ALSO HAD AN ACCENT OF A 'SOUTHERN COUNTRY' NATURE. THE COMBINATION OF THE TWO MADE HIM VERY DIFFICULT TO UNDERSTAND. AFTER ASKING THE TWR TO 'SAY AGAIN;' I EXPECTED TO RECEIVE CLRER INSTRUCTIONS FROM THE TWR. BUT THE SECOND XMISSION WAS ALMOST IDENTICAL TO THE FIRST WITH THE ADDITION OF 'TFC ON A 4 MI FINAL.' IF THE INSTRUCTIONS WERE 'HOLD SHORT;' OR 'TAXI INTO POS AND HOLD;' THEY WERE GIVEN IN A FORMAT THAT COULD NOT BE UNDERSTOOD. AFTER THINKING ABOUT WHAT HAPPENED AND TALKING TO AN INSTRUCTOR; I CAME TO REALIZE THE CTLR MIGHT HAVE WANTED ME TO 'POS AND HOLD.' IF THAT WAS THE CASE; WHAT I HEARD WAS 'ZISHINANHO.' WITH 'TFC ON A 4 MI FINAL' (C130); PULLING OUT ONTO A RWY AND SITTING THERE DID PRESENT ITSELF AS THE CORRECT THING TO DO. THIS INCIDENT WAS INADVERTENT AND NOT DELIBERATE; AND WAS CAUSED BY UNNECESSARY RAPID SPEECH THAT LED TO CONJOINING OF THE PHRASE. THE USE OF CLRLY ENUNCIATED STANDARD INSTRUCTIONS; SUCH AS 'TAXI INTO POS AND HOLD;' 'HOLD SHORT OF RWY;' 'CLRED FOR TKOF;' WOULD HAVE PREVENTED THIS SIT.