Habal al-habalah means that a she-camel delivers an offspring and then the offspring which it delivers becomes pregnant.
عَنِ النَّبِيِّ ﷺ نَحْوَهُ وَقَالَ حَبَلُ الْحَبَلَةِ أَنْ تُنْتَجَ النَّاقَةُ بَطْنَهَا ثُمَّ تَحْمِلُ الَّتِي نُتِجَتْ
In the pre-lslamic period of ignorance the people used to bargain with the meat of camels on the principle of Habal-al-Habala which meant the sale of a she-camel that would be born by a she-camel that had not yet been born. The Prophet ﷺ forbade them such a transaction.
كَانَ أَهْلُ الْجَاهِلِيَّةِ يَتَبَايَعُونَ لُحُومَ الْجَزُورِ إِلَى حَبَلِ الْحَبَلَةِ قَالَ وَحَبَلُ الْحَبَلَةِ أَنْ تُنْتَجَ النَّاقَةُ مَا فِي بَطْنِهَا ثُمَّ تَحْمِلَ الَّتِي نُتِجَتْ فَنَهَاهُمُ النَّبِيُّ ﷺ عَنْ ذَلِكَ