1. What does "Sahira" mean in Quranic Arabic?;
2. If it has a bad meaning then should I change it?.
Sihr (magic, witchcraft) is a word used to describe spells, incantations and knots [used for purposes of witchcraft] which have an effect on people’s hearts and bodies, so that may cause sickness, kill or cause division between a man and his wife. Allaah says (interpretation of the meaning):
“And from these (angels) people learn that by which they cause separation between man and his wife”
Sihr is a devilish action, most of which is only achieved by means of shirk and drawing close to the shayaateen (devils) by means of that which they love.
The saahir (practitioner of witchcraft) is the one who does this action. The word Saahirah describes a woman who does that.
Allaah says (interpretation of the meaning):
“And from the evil of those who practise witchcraft when they blow in the knots”
This is a references to female witches (sawaahir pl. of saahirah).
Sihr is a major sin. Allaah says (interpretation of the meaning):
“and the magician will never be successful, to whatever amount (of skill) he may attain”
The Prophet (peace and blessings of Allaah be upon him) said: “Avoid the seven sins which doom a person to Hell” – among which he mentioned sihr (witchcraft).
Narrated by al-Bukhaari, 2767; Muslim, 89.
The word sihr is sometimes used to refer to permissible things such as eloquence and the ability to express oneself in a clear and moving manner, which stirs people’s hearts, as in the words of the Prophet (peace and blessings of Allaah be upon him): “Some eloquent speech is as effective as magic.”
Whatever the case, it is preferable to change this name, but you must avoid names which may have false meanings or which may cause confusion or lead to the person being accused. The Prophet (peace and blessings of Allaah be upon him) used to change ugly names to good names.
See question no. 14622, Is it obligatory to change a name if it is not good?
It was narrated from Ibn ‘Umar that ‘Umar had a daughter whose name was ‘Aasiyah (meaning disobedient). The Messenger of Allaah (peace and blessings of Allaah be upon him) named her Jameelah instead. Narrated by Muslim, 2139.
Names carry meanings, as it is said, and everyone is influenced by his name. So we are required to choose good names that have meanings.
And Allaah knows best.