What is the meaning of the word “Laavan” and it’s history?

Laavan are for the union of soul with the Akal Purkh. Both male and female have to be committed to the teachings of Gurbani

ਹਰਿ ਪਹਿਲੜੀ ਲਾਵ ਪਰਵਿਰਤੀ ਕਰਮ ਦ੍ਰਿੜਾਇਆ ਬਲਿ ਰਾਮ ਜੀਉ ॥ – 773

Firmness with the Shabad are specifically required.
The relation of Affection love have to genrated by praises of Akal Purkh and acquiring His qualities.
ਨਿਰਮਲੁ ਭਉ ਪਾਇਆ ਹਰਿ ਗੁਣ ਗਾਇਆ ਹਰਿ ਵੇਖੈ ਰਾਮੁ ਹਦੂਰੇ ॥ – 774

Mind should be filled with divine love and desire to meet Akal Purkh
ਜਨੁ ਨਾਨਕੁ ਬੋਲੇ ਤੀਜੀ ਲਾਵੈ ਹਰਿ ਉਪਜੈ ਮਨਿ ਬੈਰਾਗੁ ਜੀਉ ॥੩॥- 774

Constant attachment with Akal Purkh is required all the time through the Shabad Guru
ਹਰਿ ਮੀਠਾ ਲਾਇਆ ਮੇਰੇ ਪ੍ਰਭ ਭਾਇਆ ਅਨਦਿਨੁ ਹਰਿ ਲਿਵ ਲਾਈ ॥ 774

Then only one can be one with the Akal Purkh.
ਜਨੁ ਨਾਨਕੁ ਬੋਲੇ ਚਉਥੀ ਲਾਵੈ ਹਰਿ ਪਾਇਆ ਪ੍ਰਭੁ ਅਵਿਨਾਸੀ ॥੪॥੨॥- 774

Once both husband and wife are one with Akal Purkh with the help of Gurbani. They will have same opinion with the help of Gurbani. Then they will be able to develop a successful family system.

ਏਕ ਜੋਤਿ ਦੁਇ ਮੂਰਤੀ ਧਨ ਪਿਰੁ ਕਹੀਐ ਸੋਇ ॥੩॥ – 788

Please go through the following article for details

http://www.geocities.ws/sarbjitsingh/Bani3840GurMag201003.pdf