'Had' is the past form as well as the past participle of 'have'.
The first sentence is in the simple past tense which typically has this form:
Subject + past form of verb
I had (past tense of have) a bad day.
I reached (past tense form of 'reach') the office late.
The simple past is used normally to denote an action that is completed in the past.
The second sentence is in the past perfect tense which has this form:
Subject + had + past participle of verb
If two non-consecutive events happened in the past, this tense is used to show the first event.
By the time we arrived, the party had begun.
= The party began. Then we arrived.
By the time we arrived, they had eaten all the food!
= They ate all the food; then we arrived.
I had had a bad day already, and I arrived home to find that it had been robbed!
= I was having a bad day. During the day my home was robbed. Then I arrived home and found out about the robbery.
Refer to Kajaco's example as well. Here, the past perfect is used to show which incident/action happened first.
It means she suddenly stood up or jumped to her feet, probably in amazement.
EDIT
According to the OED, start could mean:
3 [ no obj. ] jerk or give a small jump from surprise or alarm: ‘Oh my!’ she said, starting.
• [ no obj., with adverbial of direction ] literary move or appear suddenly: she had seen Meg start suddenly from a thicket.
Best Answer
Nobody knows for sure.
The Greek phrase is “ἔπεα πτερόεντα”, and “winged words” is a literal translation. The idiomatic meaning of this expression is not known, and it has spurred considerable debate amongst translators and scholars.
Herbert Jordan, who translated Homer into English, shares some of the issues he encountered on his website. He discusses winged words.
A common school of thought is that “winged words” connote speed in some manner — either emphasizing the spontaneity of the words, or indicating that the words were spoken quickly. This interpretation is found amongst ancient and modern studies¹. George Calhoun contended that winged words were spoken with unusual emotion or intensity. At the other end of the spectrum his student Milman Parry held that the words held no particular meaning and that Homer “uses this phrase just because it is useful, and without thought for any particular meaning which the epithet ‘winged’ might have”. Winged words played an important role in the elaboration of some theories about oral traditions.
Some translators have translated the phrase literally, others have reflected a perceived emotion, yet others ignored these words.
Incidentally, the expression “winged words” has come to mean a phrase that started as a quote but then took a life of its own. The very coining of this usage by Georg Büchmann made “winged words” winged words.
¹ F. M. Combellack, Words that Die. The Classical Journal, 1950.
² M. Parry, About Winged Words. The Classical Journal, 1937.